A. Field of the Invention
This invention relates to the field of wheels and brakes for wheelchairs. More particularly, this invention relates to a lightweight wheel and brake assembly including an injection-moldable fiber-reinforced plastic push rim, injection-moldable fiber-reinforced plastic wedge-bottom spokes, and a lockable static in-hub brake.
B. The Background Art
Typical prior art rear wheelchair wheels typically include a steel rim, a steel push ring, a steel hub, steel spokes, a rubber tire and tube, and a lever positionable against the tire to serve as a brake. Prior art wheelchair wheel assembles typically weigh 12 to 14 pounds per pair. Because users of wheelchairs frequently suffer from a weakened physical condition, this weight can be a great burden to both the user of the wheelchair and to other persons pushing or lifting the wheelchair. As a result, wheel assemblies have become a target for those interested in designing a lighter wheelchair. Aluminum alloy wheels including an aluminum push ring, an aluminum rim, an aluminum hub, steel spokes, a rubber tire and tube and brass nipples are the preferred light weight prior art wheel chair wheel assembly, usually weighing 71/2 to 9 pounds per pair. The wheelchair wheel assembly of the present invention weighs only 5.5 pounds per pair, a 61% reduction in weight over prior art steel wheels assemblies and a 39% reduction in weight over aluminum alloy wheel assemblies. This weight reduction can result in substantial gains in mobility for the wheelchair user, not only in the use of the wheelchair, but also in lifting the wheelchair to place it into an automobile.
Another problem with prior art wheelchair wheel assemblies is that they transmit most vibrations and shock from the ground over which the wheelchair is travelling to the wheelchair rider, doing little to absorb such shock or vibration, particularly if a solid rather than a pneumatic tire is used. Vibrations and shocks are transmitted from the ground through the wheelchair wheel assembly and into the wheelchair frame jostling, shaking, vibrating and bouncing the rider in the wheelchair. Users of wheelchairs often suffer from pre-existing spinal injuries, pressure sores, skin abrasions, and other maladies and discomforts, as well as being generally injury-prone, and cannot tolerate the additional trauma of riding in a wheelchair that provides a bumpy, vibrating ride. The trauma of such a ride can aggravate existing conditions and cause further injury. The wheelchair wheels of this invention reduce the transmission of vibrations and shocks through a dampening action inherent in some materials such as fiber-reinforced plastic or composite materials.
Another problem with prior art wheelchair wheel assemblies is that they are difficult to statically brake or lock into position at times when the rider or attendant does not want the wheelchair to roll. Prior art attempts to accomplish this with a "brake" that consists of a mechanism with a bar or plate that indents into the tire to hold the wheelchair in place, the other end of the mechanism being attached to the wheelchair frame. The prior art brakes are heavy, being made of weighty steel components. The prior art brakes are also difficult for many riders to operate because significant hand strength is required to operate the brake mechanism. Prior art brakes are usually located in a difficult to reach location on the wheelchair, making their use doubly problematic for most wheelchair users. And prior art brakes are only partially effective at positively securing a wheelchair in place--only a small amount of force is required to roll a wheelchair with a prior art brake applied.
The wheelchair wheel assembly of this invention includes an optional brake that is located inside the wheel hub, with a handle conveniently located on the outside of the hub. The brake of the present invention is effective, requiring substantial force to roll the wheels when the brake of the invention is engaged. The brake is easy to operate, in that very little force or strength is required to manipulate the handle to engage the brake and the brake is very light weight in comparison with prior art brakes.